Semiconductor device and fabrication method for the same

Abstract

The semiconductor device includes a first transistor and a second transistor formed in a semiconductor substrate. The first transistor includes: a first gate insulating film formed on the semiconductor substrate; and a first gate electrode formed on the first gate insulating film. The second transistor includes: a second gate insulating film formed on the semiconductor substrate; and a second gate electrode formed on the second gate insulating film. The first gate insulating film includes a first insulating material with a first element diffused therein, the second gate insulating film includes the first insulating material, and the amount of the first element contained in the first gate insulating film is greater than the amount of the first element contained in the second gate insulating film.

1. A fabrication method for a semiconductor device, comprising the steps of:
 (a) forming an insulating film and a first electrode film sequentially in this order on the entire surface of a semiconductor substrate having a first region and a second region; 
 (b) removing a portion of the first electrode film formed on the first region; 
 (c) forming a first cap film containing a first element over the semiconductor substrate and thereafter subjecting the resultant substrate to heat treatment after the step (b), to allow the first element to diffuse into a portion of the insulating film formed on the first region and at least a top portion of the first electrode film; 
 (d) forming a second electrode film over the semiconductor substrate after the step (c); and 
 (e) etching at least the second electrode film and the insulating film, to form a first gate insulating film including the insulating film with the first element diffused therein and a first gate electrode including the second electrode film on the first region, and form a second gate insulating film including the insulating film and a second gate electrode including the second electrode film on the second region. 
 
     
     
       2. The fabrication method for a semiconductor device of  claim 1 , further comprising the step of (f) removing together with the first cap film a region of the first electrode film containing the first element diffused therein before the step (c) and after the step (d),
 wherein in the step (e), the second gate electrode including the second electrode film and the remainder of the first electrode film is formed. 
 
     
     
       3. The fabrication method for a semiconductor device of  claim 1 , wherein in the step (a), a second cap film containing a second element is formed between the insulating film and the first electrode film, and
 in the step (e), the second gate insulating film including the insulating film and the second cap film is formed. 
 
     
     
       4. The fabrication method for a semiconductor device of  claim 3 , wherein the second element is aluminum or tantalum. 
     
     
       5. The fabrication method for a semiconductor device of  claim 1 , further comprising the step of (g) removing the first cap film and the first electrode film between the step (c) and the step (d),
 wherein in the step (d), a second cap film containing a second element is formed over the semiconductor substrate, and then the second electrode film is formed, and 
 in the step (e), the first gate insulating film including the insulating film with the first element diffused therein and the second cap film is formed, and the second gate insulating film including the insulating film and the second cap film is formed. 
 
     
     
       6. The fabrication method for a semiconductor device of  claim 1 , further comprising the steps of:
 (h) removing together with the first cap film a region of the first electrode film containing the first element diffused therein in the second region after the step (c) and before the step (d); and 
 (i) removing a part where the first electrode film remains in the second region after the step (i) and before the step (d), 
 wherein in the step (a), a second cap film containing a second element is formed between the insulating film and the first electrode film, and 
 in the step (e), the second gate insulating film including the insulating film and the second cap film is formed. 
 
     
     
       7. The fabrication method form a semiconductor device of  claim 6 , wherein the step (h) and the step (i) is a continuous single step. 
     
     
       8. The fabrication method for a semiconductor device of  claim 1 , wherein the first element is lanthanum. 
     
     
       9. The fabrication method for a semiconductor device of  claim 1 , wherein the first electrode film and the second electrode film are made of titanium nitride. 
     
     
       10. A fabrication method for a semiconductor device, comprising the steps of:
 (a) forming an insulating film, a first electrode film, and a hard mask sequentially in this order on the entire surface of a semiconductor substrate having a first region and a second region; 
 (b) removing a portion of the hard mask formed on the first region; 
 (c) forming a first cap film containing a first element over the semiconductor substrate and thereafter subjecting the resultant substrate to heat treatment after the step (b), to allow the first element to diffuse into a portion of the insulating film formed on the first region and at least a top portion of the hard mask; 
 (d) removing the first cap film and the hard mask after the step (c); 
 (e) forming a second electrode film over the semiconductor substrate after the step (d); and 
 (f) etching at least the second electrode film, the first electrode film, and the insulating film, to form a first gate insulating film including the insulating film with the first element diffused therein and a first gate electrode including the second electrode film on the first region, and form a second gate insulating film including the insulating film and a second gate electrode including the second electrode film and the first electrode film on the second region. 
 
     
     
       11. The fabrication method for a semiconductor device of  claim 10 , wherein in the step (a), a second cap film containing a second element is formed between the insulating film and the first electrode film, and
 in the step (f), the second gate insulating film including the insulating film and the second cap film is formed. 
 
     
     
       12. The fabrication method for a semiconductor device of  claim 11 , wherein the second element is aluminum or tantalum. 
     
     
       13. The fabrication method for a semiconductor device of  claim 10 , further comprising the step of (i) removing the first electrode film between the step (d) and the step (e),
 wherein in the step (a), a second cap film containing a second element is formed between the insulating film and the first electrode film, and 
 in the step (f), the second gate insulating film including the insulating film and the second cap film is formed.